• We would like to remind our members that this is a privately owned, run and supported forum. You are here at the invitation and discretion of the owners. As such, rules and standards of conduct will be applied that help keep this forum functioning as the owners desire. These include, but are not limited to, removing content and even access to the forum.

    Please give yourself a refresher on the forum rules you agreed to follow when you signed up.

Fractal Audio AMP models: USA IIC+ and IIC++ (MESA/Boogie Mark IIC+)

yek

Moderator
Moderator


USA IIC+ / IIC++: based on MESA/Boogie Mark IIC+

MESA/Boogie is a famous amp manufacturer, founded by Randall Smith in ‘71 in California. Company information.

Some of the amps carry the MESA name while others have a MESA/Boogie label.​

Randal Smith started off with the “snakeskin” Boogie amp, a modded Fender Princeton with increased gain and sustain, which made Santana famous (or was it the other way around?), now known as Mark I. It was recently re-issued.

The series has evolved. No longer called Boogie, they’re now referred to as the Mark series. Mainly known for their smooth high-gain tones, loved by metalheads as well as fusion guitar players. John Petrucci (Dream Theater) is probably their most famous endorser. Metallica are also known for their use of the IIC+. The current Mark model is the Mark Five.

Cliff:
"I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different."​

We’ve got models of the legendary Mark IIC+, IIC++, and IV. This post is about the IIC+, the amp that introduced guitar players to liquid and smooth lead tones, and scooped high-gain.

MESA:
"And YES… it’s a MARK IIC+! A next generation Re-Issue of the legendary amp so many Recording Artists, MESA enthusiasts and Tone Freaks the world over covet, often searching high and low to find."​

The quote above refers to the JP-2C, John Petrucci’s signature amp, demonstrating that the Mark IIC+ still is king of the hill.

Wikipedia:
"The Mark IIC also featured a new Pull Bass shift on the front panel, which slightly extended the low frequencies in the preamp.​

The Mark IIC+ was the last of the Mark II series and featured a more sensitive lead channel, because it features a dual cascading drive stage, whereas the IIA and IIB had a single stage drive circuit.​

Some owners/dealers/sellers say the "+" refers to an amp having an EQ, but they are mistaken. The mistake may have originated in the mid 1980s, when Mesa/Boogie issued their Studio .22 model and then changed the name to Studio .22+, which featured improved wiring, etc. All the Mark II models could be made with EQ as an option, but not all of them did. A Mark IIC+ could, for example, refer to a 100 watt amp without EQ or reverb.​

One can tell if a particular amp is a "+" by looking for a hand-written black "+" mark directly above where the power cord attaches to the back of the amp. Many dealers increase the price on a Mark IIC+ but often don't know anything about what the "+" means--they often don't even know where to find the "+" mark. Indeed, the mark itself can be forged. An owner can call Mesa/Boogie and ask them to check his or her serial number against their records. Mesa/Boogie only made about 1,400 Mark IIC amps before going to the Mark IIC+. Another cosmetic way of distinguishing a IIC from a IIC+ is the front panel. A IIC has the traditional "Gain Boost" pull switch integrated into the master volume, while a IIC+ replaced the switch with a Pull Deep bass booster.​

The Mark IIC+ Is currently the most coveted vintage Boogie, selling for twice its original price on average, because of its much praised "Liquid Lead" mode, and also, its warm, clean rhythm mode.”​

Review in Vintage Guitar.

The modeled IIC+ is a version WITHOUT a graphic EQ. Don’t cry, see post #2. Unlike the original amp, you can use the GEQ in the models.

The original amp operates in Class-A (2 power tubes) or Simul-Class (2 power tubes in Class-A and the other two in Class A/B). It has been modeled in Simul-Class mode.

Cliff:
"If you want the sound of the non-SimulClass version set Triode 1 Plate Freq to 1350 Hz."​

It has a single input, 6L6 power tubes, reverb and 2 channels: Rhythm and Lead.

The main controls are Volume (pull: Bright), Treble (pull: Shift = Fat), Bass (pull: Shift), Middle, Presence, Master rhythm (pull: Deep), Lead Drive and Master Lead (pull: Bright).

Cliff:
"The Pull Bright on the Volume knob is the classic "Bright Cap" which engages a capacitor across the potentiometer. This is already modeled in the Axe-Fx via the Bright Switch. The Pull Bright on the Lead Master knob engages a 0.22uF cap on the cathode of the last triode in the overdrive circuit. As there is no switch for this in the Axe-Fx it requires a separate model. Cathode caps are very common in tube amps. If the value is large the stage has more gain and the response is relatively flat. If the value is small the stage has more gain at higher frequencies. Amp designers use cathode caps to shape the frequency response. Caps in the range of 0.1 to 1.0 uF are commonly used to reduce bass response. A cathode cap works by decreasing the amount of negative feedback through shunting higher frequencies to ground. This reduced negative feedback increases the gain (and reduces linearity). FWIW the Axe-Fx is the only modeler of which I'm aware that actually models triodes using a feedback technique. Other modelers use static waveshapers. The Axe-Fx triode models incorporate feedback so if there is a virtual cathode cap the stage is less linear in addition to having more gain."​

Cliff:
"The key to a good Boogie sound, IMO, is the Fat Switch. This is the Treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."​

"The IIC+ does not have a gain boost and doesn't need one. There is plenty of gain. The Pull Deep switch engages a large cathode cap on the final triode stage. With Pull Deep off there is actually a shelving response into the power amp (bass is reduced)."​

"To emulate Pull Shift on the Bass control: "Put a Tilt EQ before the amp block with a frequency of 320 Hz and a gain of -3 dB. Set the Level to +3 dB".​

Here’s the original “repair” manual.

The Rhythm (clean) channel hasn’t been modeled, so the models all refer to the Lead channel.

USA IIC+: Lead Master Pull Bright off, Pull Deep off

USA IIC+ Bright: Lead Master Pull Bright on, Pull Deep off

USA IIC+ Deep: Lead Master Pull Bright off, Pull Deep on

USA IIC+ BRT/DP: Lead Master Pull Bright on, Pull Deep on

The IIC+ doesn’t have features as the Mark IV or V. Still, it isn’t easy to dial in. Cliff’s guidelines to dial in the IIC+:

“The old version of the model incorrectly referenced the Mark IV tone stack. These tone stacks are identical except for the taper of the mid pot. The IIC+ has a linear pot and the Mark IV has a Log10 pot. I had it backwards in my earlier comments. My guess is that Mesa found that turning the midrange down sounds best (and it does) so they changed the pot taper to do this automatically since noon on a Log10 pot is equal to a 1.0 on a linear pot.

Commensurate with (1) I found myself turning the midrange down as well as the bass and turning the treble up.

I think the default Master Volume value is a bit high so you may want to turn that down. I've reduced the default for Quantum 2.03.

Turn the bright switch on. Every bit of information I've found says that people typically used the Pull Bright on the Volume knob. This is equivalent to the Bright switch under the Treble control on the model. I always turn it on and I've set it on by default for Q2.03.

USE THE EQ. The tone stack is pre-distortion which is atypical for a high-gain amp. Tone stacks are almost always post-distortion. Since the tone stack is pre-distortion you need to do your post distortion tone shaping using the EQ. The tone controls set the feel and the distortion texture, the EQ shapes the final tone. I like to do a gentle V-curve.

These were my settings for a killer high-gain tone: Model: USA IIC+ / Input Drive: 8.1 / Overdrive: 9-10 / Bass: 1.0 / Midrange: 1.8 / Treble: 8.9 / Presence: 4.5 / MV: 4.0 / Level: -20 dB / Bright Switch ON / 80 Hz: 4.8 / 240 Hz: 2.6 / 750 Hz: -4.5 / 2200: -0.2 / 6600: 0."​

For another take on the IIC+ sound, try the USA PRE Yellow model. This is the IIC+ mode of MESA’s Triaxis preamp. It has Pull Shift and Pull Bright enabled by default. Some players find this model easier to dial in (and some actually prefer its sound to the IIC+).

Quantum firmware 3.03 brought us the "Metallica's IIC++" model. The details are sparse. It's the model used by Metallica for their live sound. Whether this model is based on one of the rare real IIC++ amps, has not been disclosed.

MESA equipped the IIC+ with EV-12L speakers. Try stock cab #105. Red Wire sells IRs of original IIC+ cabinets. Alt. try stocks cabs #19 and #150, Rectifier/V30 cabinets or cab #108 (Petrucci’s own cab with V30s).
 
Last edited:

yek

Moderator
Moderator
Background on the IIC+ without graphic EQ:

"Back when I was testing II C+’s every day in the burn-in room, I always thought the non-graphic amps had a certain attack and purity to the sound that the amps that had Graphic EQ on them just didn’t have. There was an urgency and bold punch to the sound…they seemed tighter and more cohesive. Now granted, we made far more amps with the on-board EQ than without…probably 70% had the EQ, but not many people had the opportunity to compare day-in and day-out as I did. The EQ model had the shaping advantage…no doubt about it, and certainly all the sounds that II C+ are famous for were created with the EQ being an integral part of that sound, but when it came to the straight sound – no EQ – the non-graph model always got to me with it’s speed and authority. So it was that I came to be the obsessive/compulsive owner of no less than 8 of the II C+ Simul-Class, Reverb (non-graphic) heads. I hand picked these as being the best sounding amps - for me - out of the thousands of II C+ we made. Out of these eight amps I immediately found my favorite - which I dubbed “His Highness the C-ness” and which I used as a reference model to have our Chief Tech and Archival Guru Michael Bendinelli, copy exactly on the other 7 amps. Everything was measured and scrutinized (pot values, resistors, caps, transformers swapped, etc.) and duplicated, and in the end… all 8 sounded alike. (...) In our endless comparisons of many original II C+’s - both EQ and non-EQ samples - alongside this golden reference, we discovered that I wasn’t just Tone-dreaming. There was actually a difference between the EQ model and those non-EQ models. It all came down to a coupling capacitor at the end of the EQ circuit that feeds the driver. In the EQ model, it was a great big cap that let a lot of sub-low pass, slowing down the sound and making it fatter. In my amp - a non-EQ version - this cap was smaller and didn’t let as much sub-low through - which speeds up the sound and makes everything tighter and more urgent. There it was, a simple part…but it made all the difference in the time domain. Yet there were so many more of these slower, fatter sounding EQ versions out in the world… that many more people were used to hearing as their reference. It would not do well to set the MARK V permanently to this faster, tighter way. Too many players would have a tough time adjusting and when they compared the two amps side by side, the V would sound faster and tighter yes, but also stripped of sub-low and therefore maybe not as fat in comparison to their trusty II C+ Graphic model or MARK IV - which also had the bigger coupling cap." (Douglas West)
 

Genome

Inspired
Two awesome IIC+ clips, again heavy, one is a playthrough vid for your tonematching pleasure

 

shotgunn

Fractal Fanatic
Background on the IIC+ without graphic EQ:

"Back when I was testing II C+’s every day in the burn-in room, I always thought the non-graphic amps had a certain attack and purity to the sound that the amps that had Graphic EQ on them just didn’t have. There was an urgency and bold punch to the sound…they seemed tighter and more cohesive. Now granted, we made far more amps with the on-board EQ than without…probably 70% had the EQ, but not many people had the opportunity to compare day-in and day-out as I did. The EQ model had the shaping advantage…no doubt about it, and certainly all the sounds that II C+ are famous for were created with the EQ being an integral part of that sound, but when it came to the straight sound – no EQ – the non-graph model always got to me with it’s speed and authority. So it was that I came to be the obsessive/compulsive owner of no less than 8 of the II C+ Simul-Class, Reverb (non-graphic) heads. I hand picked these as being the best sounding amps - for me - out of the thousands of II C+ we made. Out of these eight amps I immediately found my favorite - which I dubbed “His Highness the C-ness” and which I used as a reference model to have our Chief Tech and Archival Guru Michael Bendinelli, copy exactly on the other 7 amps. Everything was measured and scrutinized (pot values, resistors, caps, transformers swapped, etc.) and duplicated, and in the end… all 8 sounded alike. (...) In our endless comparisons of many original II C+’s - both EQ and non-EQ samples - alongside this golden reference, we discovered that I wasn’t just Tone-dreaming. There was actually a difference between the EQ model and those non-EQ models. It all came down to a coupling capacitor at the end of the EQ circuit that feeds the driver. In the EQ model, it was a great big cap that let a lot of sub-low pass, slowing down the sound and making it fatter. In my amp - a non-EQ version - this cap was smaller and didn’t let as much sub-low through - which speeds up the sound and makes everything tighter and more urgent. There it was, a simple part…but it made all the difference in the time domain. Yet there were so many more of these slower, fatter sounding EQ versions out in the world… that many more people were used to hearing as their reference. It would not do well to set the MARK V permanently to this faster, tighter way. Too many players would have a tough time adjusting and when they compared the two amps side by side, the V would sound faster and tighter yes, but also stripped of sub-low and therefore maybe not as fat in comparison to their trusty II C+ Graphic model or MARK IV - which also had the bigger coupling cap." (Douglas West)
This is the great post in the history of the intornets. Special thanks to Al Gore for inventing the intornets.
 

Josetxu

Inspired
Seems that Mark Knopfler used Mark IIs for Love over gold and its tour, so thats what he used for Alchemy. But the clean channel isn't modeled, what model could sound similar to that?
 

Callan

Inspired
Seems that Mark Knopfler used Mark IIs for Love over gold and its tour, so thats what he used for Alchemy. But the clean channel isn't modeled, what model could sound similar to that?
USA clean maybe ? Should be pretty close. Mark II clean / Mark IV clean.. same same.
Next to try might be USA PRE CLEAN.

Happy playing, embrace your own personal sounds / take on any given song.
 

crg123

Experienced
@yek The video you linked for for the USA Rhythm and clean (Mark IV) not the IIC++.

Sounds great but I figured I'd let you know!

I think you meant to link this video:

 
Last edited:

dumbeat

Inspired
Cliff:
"The Pull Bright on the Volume knob is the classic "Bright Cap" which engages a capacitor across the potentiometer. This is already modeled in the Axe-Fx via the Bright Switch. The Pull Bright on the Lead Master knob engages a 0.22uF cap on the cathode of the last triode in the overdrive circuit. As there is no switch for this in the Axe-Fx it requires a separate model. Cathode caps are very common in tube amps. If the value is large the stage has more gain and the response is relatively flat. If the value is small the stage has more gain at higher frequencies. Amp designers use cathode caps to shape the frequency response. Caps in the range of 0.1 to 1.0 uF are commonly used to reduce bass response. A cathode cap works by decreasing the amount of negative feedback through shunting higher frequencies to ground. This reduced negative feedback increases the gain (and reduces linearity). FWIW the Axe-Fx is the only modeler of which I'm aware that actually models triodes using a feedback technique. Other modelers use static waveshapers. The Axe-Fx triode models incorporate feedback so if there is a virtual cathode cap the stage is less linear in addition to having more gain."
Cliff:
"The key to a good Boogie sound, IMO, is the Fat Switch. This is the Treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
"The IIC+ does not have a gain boost and doesn't need one. There is plenty of gain. The Pull Deep switch engages a large cathode cap on the final triode stage. With Pull Deep off there is actually a shelving response into the power amp (bass is reduced)."
"To emulate Pull Shift on the Bass control: "Put a Tilt EQ before the amp block with a frequency of 320 Hz and a gain of -3 dB. Set the Level to +3 dB".

For people who are used to use certain amps and looking to replace them with the Models on the AxeFx (And who are not trained Amplifier technicians), it looks like you need to really learn the inside and outs of the design technicalities to even get your basic setting on, say, a IIC+.
Wouldn't it be so much more useful, fast, practical and intuitive for players who are not Amp techs to simply have each modeled amp LOOK like the original or at least labeled the same? As it is described above by Cliff, it almost feels like buying a kit and having to build your amps if it was in the real world.
 

ElectricPhase

Power User
@dumbeat Have you ever owned a Mesa Boogie Mark series amp? I have a Mark III, purchased new in 1989. It really is complex and finicky to dial in. ...and worth it when you get the good stuff. Cliff was just being thorough in letting us know what's behind the curtain.
 
Top Bottom